Internet Protocol Television (IPTV) is a service that streams multimedia content over a packet-switched network using the Internet Protocol (IP) suite. IPTV uses multicasting to stream IPTV content from a multicast source to a multicast group. Subscribers may access a particular IPTV channel multicast stream by joining a multicast group corresponding to that IPTV channel.
A group management protocol such as Internet Group Management Protocol (IGMP) is typically used for joining and leaving multicast groups in IPTV. A subscriber that wishes to access an IPTV channel multicast stream will send an IGMP Report message to a network device such as a multicast router requesting access to the IPTV channel multicast stream. The network device receives the request and performs Connection Admission Control (CAC) operations to determine whether the subscriber's request should be allowed or denied.
If the subscriber's request is allowed, then the network device operates to forward the IPTV channel multicast stream to the subscriber. The IPTV channel multicast stream is delivered over a routing path established by a multicast routing protocol such as Protocol Independent Multicast (PIM). However, if the subscriber's request is denied, then the network device may decide to drop the subscriber's IGMP Report message.
There could be several reasons for the network device to drop the subscriber's IGMP Report message. For example, the subscriber's request could be denied because the subscriber is attempting to access a pay-per-view channel or attempting to exceed a bandwidth limit. If the network device decides to drop the subscriber's IGMP Report message, the subscriber will not receive the requested IPTV channel multicast stream and the subscriber will not know why their IPTV channel request did not go through.